Mandelic acid. What it does for skin, and when a clinic peel beats a serum.

Mandelic acid is the exfoliating acid we are asked about most by people whose skin marks easily. It comes in two very different forms: a leave-on serum you use at home, commonly at up to about 10 percent, and a professional peel applied in clinic at 20 percent or more for a set time, then removed. Same molecule, different jobs.

This guide covers what mandelic acid is, what the published trials do and do not show, how to choose between a serum and a peel, and who should not use it.

What mandelic acid is, and why its size matters.

Mandelic acid is an alpha hydroxy acid (AHA), the same family as glycolic and lactic acid. It was first isolated from bitter almonds, and its name comes from Mandel, the German word for almond. AHAs loosen the bonds that hold dead cells to the surface of the skin, so those cells shed more evenly and the skin looks smoother and brighter.

What sets mandelic acid apart is size. Its molecule weighs about 152 daltons, roughly twice glycolic acid's 76. A larger molecule moves into the skin more slowly and more evenly, which is why mandelic acid has a reputation for a gentler exfoliation profile. Slower is the point: fewer peaks of irritation, and in skin that marks easily, fewer chances to leave a mark.

It is also studied for acne. In one trial the authors chose it partly for its reported antibacterial and anti-inflammatory properties (Dayal, Kalra and Sahu, 2020).

What the trials show, and what they do not.

The trials are small and were run in Indian patients. They support mandelic acid as a gentler option for acne and marks. They do not show that it outperforms everything else.

• Acne and post-acne marks. In 44 people, a combination peel of 20% salicylic and 10% mandelic acid gave greater improvement in active acne and post-acne hyperpigmentation than a 35% glycolic peel over six sessions, with fewer side effects (Garg, Sinha and Sarkar, 2009).
• Melasma. In 90 people, the same combination peel matched a 35% glycolic peel, with melasma scores falling by about 61 and 62 percent after 12 weeks, and both were ahead of a phytic acid peel. Every group was prepared with hydroquinone and tretinoin first, which is not how we start (Sarkar et al., 2016).
• Acne. In 50 people, a 45% mandelic peel matched a 30% salicylic peel overall. Salicylic did more for blackheads and whiteheads, mandelic more for inflamed spots, and mandelic had fewer adverse effects (Dayal, Kalra and Sahu, 2020).

Two of the three used mandelic acid combined with salicylic acid, and all three used strengths well above an at-home serum. A 2026 scoping review of chemical peels in skin of colour found only seven studies that met its criteria and called the evidence limited by small samples and short follow-up (Garelick et al., 2026). The honest reading: a gentle option with reasonable evidence for acne and marks, at clinic strengths, over a course. Individual results vary.

Serum or clinic peel: which one, and when.

A serum and a peel are not competitors. A serum is low strength and used regularly at home; it keeps skin turning over gently. A peel is a higher concentration applied for a set time by a clinician, then removed; it does more in one session, and it is where a patch test and a plan matter.

• A serum makes sense if your skin is new to acids and not reactive, the concern is mild dullness or the odd blocked pore, or you want maintenance between treatments.
• A clinic peel makes sense if marks left by spots have lasted for months, you have breakouts and marks together, your skin has reacted to acids before and you want the strength chosen for you, or you want a planned course with a patch test.
• See a clinician first for melasma (a peel is not where we start; see our melasma guide), active inflamed acne or broken skin, or isotretinoin in the last 12 months.

At Melatone™ the Even Tone peel is 20% mandelic acid with citric acid and soothing aloe vera: £120 a session, or £297 for a course of three paid upfront (£99 a session). It follows a consultation and a patch test and is delivered by Arman Zaki, GMC-registered Physician Associate.

Deeper skin tones: gentler still needs a plan.

Any exfoliation that irritates the skin can leave post-inflammatory hyperpigmentation, and in Fitzpatrick IV to VI skin those marks tend to be darker and slower to fade. Mandelic acid's slower penetration is why it is often chosen first, but it still needs a patch test, a conservative start and daily sun protection.

A 2024 systematic review of post-inflammatory hyperpigmentation in skin of colour found chemical peels among the treatments with less effective outcomes overall (Mar et al., 2024). That is why, for pigmentation, a peel sits inside a plan led by sun protection and never stands in for one. Our aim is to even tone, never to lighten or bleach.

Who should not use mandelic acid, and when to pause it.

• Nut allergy. Mandelic acid was first derived from bitter almonds, and our peel's supplier advises against it for anyone with a nut allergy. For a serum, check with the brand.
• Pregnancy and breastfeeding. We do not carry out chemical peels during pregnancy or while breastfeeding. For at-home acids, ask your midwife, GP or pharmacist.
• Isotretinoin in the last 12 months, an active skin infection or cold sore, sunburn, or broken skin on the area.
• Retinoids and other acids. We ask you to stop them for a few days before a peel and for 7 days after it.

Using a mandelic serum at home. Slowly.

Start two or three nights a week on clean, dry skin, and do not use it on the same night as a retinoid while your skin is getting used to it. Wear a broad spectrum SPF every morning. Stop if stinging lasts, the skin stays red or dark patches appear, and tell your clinician. Leave it out for the week before and the week after an in-clinic peel.

Frequently asked questions